California's leadership is needed now more than ever to address the risks of a dangerously warming climate.

California's continued leadership is needed now more than ever to address the risks of a dangerously warming climate.

The science is clear that human activity is the dominant cause of global warming over the last half-century. If heat-trapping emissions continue to rise, the scope and severity of impacts will accelerate. Communities across California are already being forced to cope with increased wildfires, more frequent and extreme heat waves, a strained water management system, growing risks to agricultural crops, greater summer electricity demand, and more coastal flooding.

While we must adapt to those impacts of climate change that cannot be avoided, California must also continue to take ambitious steps to reduce its heat-trapping emissions. California deserves tremendous credit for putting innovative climate policies into practice, spurring investment, innovation, and jobs in a growing "green technology" sector. The state is well positioned to maintain its leadership in this effort.

We urge you to take decisive action this year to ensure that California:

increases its share of electricity generated from renewable sources to 50 percent by 2030; and

reduces petroleum use in the transportation sector 50 percent by 2030.

These objectives are currently reflected in two bills before the California state legislature: Senate Bills 32 and 350. As scientists and researchers with expertise in climate change, its impacts, and its solutions, we ask you to support policies that will ensure California meets these goals.

This letter was open to scientists, researchers, and economists with a Ph.D. whose peer-reviewed research focuses on the causes of climate change, the impacts of climate change, or solutions to climate change.